1. Field of the Invention
This invention generally relates to a fluid pressure type booster device of a type having a housing and a slide member. The housing includes an input port connected to a fluid pressure source, a release port connected to a fluid tank, and an output port connected to a fluid pressure apparatus. The slide member has a front surface facing a reaction chamber leading to the output port and is slidably fitted in the housing for movement between an advanced position to place the input port in communication with the output port and a retracted position to place the release port in communication with the output port. A pressure chamber is defined in the housing, which chamber is capable of generating a fluid pressure in response to operation of an operating member and which faces a back surface of the slide member or an interlocking member operatively connected to the slide member.
2. Description of the Prior Art
Such a conventional device is already known as disclosed in Japanese Patent Application Laid-open No. 116346/87. According to such prior art device, fluid pressure generated in a master cylinder by depression of a brake pedal is applied to a back surface of a piston which is coaxially abutted against a back surface of a slide member slidably fitted in a housing, and the slide member is movable in front and rear directions by a balance between a pressure acting on the back surface of the piston and a reaction force acting on the front surface of the slide member, thereby applying an amplified fluid pressure to a fluid pressure apparatus. The brake pedal is also referred to hereafter as an operating member.
In the prior art device, however, since the housing and the master cylinder are formed as separate parts, it is necessary to provide a piping for connecting the pressure chamber in the housing and the master cylinder and thus, it is difficult to make the structure compact. Further, since the pressure is applied to the pressure chamber from an initial stage of operation, the friction force of a seal member between the housing and the slide member or an interlocking member operatively connected to the slide member becomes relatively large in accordance with the pressure acting on the seal member and therefore, the operating force required at the initial stage of operation inevitably becomes relatively large.